I tried the iptables command, and it seems there's no firewall installed on it since it didn't work.
OK, it must have done something, if even an error message saying the command couldn't be found. Iptables is the default firewall for pretty much every linux distribution, so it is highly likely to be installed. Were you su or root when you tried the command? By default, iptables is usually installed in a directory only root has access to.
If you don't have a hosts.deny, that is OK. However, you might want to run find / -name hosts.deny
just to be sure. Again, run this after becoming su so it can scan all the directories. The hosts file you posted is a different beast entirely and it probably won't concern us for this problem.
The other thing to do is to try to log in both from within and from outside your LAN and see if any information from ssh shows up in either /var/log/syslog or /var/log/messages